A heat exchanger for heating a fluid flowing through a pipe by using a combustion gas, the heat exchanger comprising:
- a body including upper and lower ends which are open and having a space formed in the body to allow the combustion gas to pass through the space, the body comprising a front plate and a rear plate, and a left passage cap and a right passage cap coupled to opposite side ends of the front plate and the rear plate;
- a combustor formed in an upper portion of the space in which combustion of the combustion gas occurs;
- a heat exchange portion formed below the combustor and provided with a heat exchange pipe configured to heat an fluid by using the combustion gas;
- and
- a plurality of heat return pipes provided outside the space so as to be in contact with an outer surface of the body, the plurality of heat return pipes being spaced apart from each other in a height direction of the body,
- wherein the body comprises:
- an inlet formed at one of the left passage cap or the right passage cap and guiding inflow of the fluid into one of the left passage cap and the right passage cap;
- a concave portion formed at the front plate and the rear plate to protrude concavely inward so as to correspond to a shape of an outer circumferential surface of the plurality of heat return pipes;
- a heat-return-pipe fluid recess formed at the left passage cap or the right passage cap that includes the inlet, where the heat-return-pipe fluid recess guiding such that the fluid in a heat return pipe disposed relatively lower among the plurality of heat return pipes disposed outside the front plate is introduced to one side of the heat-return-pipe fluid recess and the fluid moves to a heat return pipe disposed relatively higher among the plurality of heat return pipes disposed outside the rear plate through another side of the heat-return-pipe fluid recess;
- and
- a recess formed between the one side of the heat-return-pipe fluid recess and the another side of the heat-return-pipe fluid recess and allowing the heat-return-pipe fluid recess to form a two-way passage structure, and
- the heat exchange pipe comprises:
- a first heat exchange pipe disposed in an upper area of the heat exchange portion to be adjacent to the combustor so as to heat the fluid by using a sensible heat of the combustion gas;
- a plurality of third heat exchange pipes disposed below the combustor to heat the fluid by using a latent heat of condensation of the combustion gas;
- and
- a resistance turbulator disposed in a third heat exchange pipe among the plurality of third heat exchange pipes that is disposed adjacent to the inlet to impart resistance to the fluid.